Method of making an extendible/expandable nozzle for rocket engines

ABSTRACT

A skirt-like device attached to the exit end of a rocket engine nozzle is fabricated of thin sheet heat resistant metal; which when extended in operative condition is in frustoconical form, but which prior to engine firing is pleat-folded inwardly into a stowed position relative to the exit end of the rocket engine nozzle. Thus, prior to engine firing the device adds little or nothing to the engine/nozzle occupancy space; but incident to engine firing the device deploys to provide an effective engine nozzle/skirt combination of increased length and exit diameter/area; said combination having an inner surface of constant slope.

CROSS REFERENCES TO RELATED PATENTS

This is a division, of application Ser. No. 637,405, filed Dec. 3, 1975now abandoned, the benefit of the filing date of which is herebyclaimed.

This application discloses subject matter relating to the art discussedin U.S. Pat. Nos. 3,183,664; 3,249,306; 3,270,504; 3,275,193; 3,346,186;3,358,933; 3,482,783; 3,494,513; 3,526,365; 3,561,679, 3,596,465;3,711,027; 3,784,109; and British Pat. No. 1,107,635.

BACKGROUND OF THE INVENTION

As is well known, the nozzle expansion of a rocket engine required formaximum thrust efficiency varies with the ambient pressure. Inmulti-stage rocket engines where a later stage is to be fired in spaceor at high altitudes, the expansion ratio is of major importance andrequires a terminal divergent exit nozzle for the rocket engine ofsubstantial length and exit diameter. However, to make a second or laterengine stage of such overall length and diameter as would be required toproduce a requisite expansion ratio would be extremely cumbersome andwasteful of otherwise usable space in the rocket assembly. Thus, it isdesirable to provide means associated with a rocket engine so that adivergent nozzle of a length and diameter suitable for maximum thrust aslow ambient pressure may be obtained by deploying such meanssubstantially coincidental to firing of the engine. In this way, theinoperative rocket engine and its accessories may be compacted so thatthe entire assembly requires a storage space no larger than thenon-extended rocket engine assembly.

BRIEF DESCRIPTION OF THE INVENTION

The invention provides a device of skirt-like form which when extendedis in the form of an annulus of frusto-conical configuration attached inmounted ring manner at its smaller diameter end to the exit of a fixedengine nozzle or to the exit of an extendible nozzle. The device isfabricated of thin sheet heat resistant metal and is adapted to bepleat-folded inwardly relative to its mounting ring portion and stowedin a retracted position relative to the engine nozzle; therebyminimizing the space occupied by the engine before firing. Wheninstalled upon a fixed nozzle type engine, upon firing of the engine theinitially developed gases impinge against the stowed skirt and push itoutwardly; whereupon the skirt unfolds and opens up to provide asmoothly continuing extension of the conical form and slope of theengine nozzle, thereby increasing the length and end diameter of theeffective nozzle, and in consequence the payload and range of theequipment.

Alternatively, the skirt of the invention may be provided as asupplement to an extendible engine nozzle, and the system so arrangedthat the gases initially developed upon engine firing (or by auxiliarysupply gas pressuring) impinge against the nozzle cover and therebydeploy the extendible nozzle portion of the engine. In such case uponjettisoning of the cover the internal gas pressures will cause the skirtto open up to provide a smoothly continuing extension of the conicalslope form of the deployed engine nozzle. Alternatively, the extendiblenozzle portion of the engine may be equipped with actuators operable bya firing sequence control system, whereby the extendible nozzle portionwill be extended after ignition of the engine. The engine exhaust plumethen peripherally engages the inner edge of the stowed skirt and drivesit outwardly, causing it to open up to provide a smoothly continuingextension of the conical slope form of the engine nozzle.

Thus, both the length of the effective nozzle and the diameter/area ofits exit end are increased; and in consequence the payload/rangeperformance capabilities of the engine are substantially improved.

THE DRAWING HEREWITH

FIG. 1 is a longitudinal sectional view showing one embodiment of thepresent invention; and illustrates the skirt device thereof as beingmounted on the exhaust end portion of an extendible rocket engine nozzleof the type shown for example in U.S. Pat. No. 3,711,027; the skirtdevice being illustrated in its stowed position within the boundaries ofthe extendible nozzle structure when in its retracted position;

FIG. 2 is a view corresponding to FIG. 1, but illustrates the enginenozzle and the auxiliary skirt device in their extended/expandedoperative position;

FIG. 3 is a fragmentary view corresponding to a portion of FIG. 1, andillustrates the flow stream lines of the engine exhaust plume prior tooperation of the extendible nozzle actuators and prior to engagement ofthe plume with the previously stowed skirt;

FIGS. 4, 5, 6, 7, are views corresponding to FIG. 3, but illustrates insequence the progressive stages of deployment of the skirt and theextendible nozzle devices; as will be explained more fully hereinafter;

FIG. 8 is a fragmentary view corresponding to a portion of FIG. 1, butillustrates adaptation of the invention to a different form of enginenozzle; the skirt device of the invention being shown in retracted"stowed" condition;

FIG. 9 is an end elevational view of the showing in FIG. 8;

FIG. 10 is a fragmentary view corresponding to FIG. 8 but illustratesthe skirt device in its deployed condition;

FIG. 11 is an end elevational view of the fragmentary showing of FIG.10;

FIG. 12 is a fragmentary sectional view corresponding somewhat to FIG.1, but showing an alternative storage arrangement including incombination an extendible/expandable primary nozzle and a skirt of thepresent invention;

FIG. 13 corresponds to FIG. 10 but illustrates the configuration of theextended/expanded nozzle and skirt combination of FIG. 12 subsequent tofiring of the rocket engine;

FIG. 14 is a fragmentary perspective view showing how a thin sheet metalworkpiece may be laid upon a die plate and crease-pressed and cutpreliminary to further fabrication into a skirt device of the presentinvention;

FIG. 15 is a fragmentary sectional view taken on line 15--15 of FIG. 14,illustrating the die pressing operation;

FIG. 16 illustrates the die-pressed and cut workpiece product of theoperation referred to in FIGS. 14, 15; and

FIG. 17 illustrates how the workpiece as illustrated at FIG. 16 isthereupon pleat-folded upon itself progressively from one end thereof tothe other preliminary to uniting the opposite ends thereof, whereby toprovide the finished skirt device in its form as shown for example atFIG. 9.

DETAILED DESCRIPTION

As shown in FIGS. 1-7 herewith, the invention may be applied to adeployable type engine nozzle such as shown for example in U.S. Pat.Nos. 3,711,027 and 3,784,109. As illustrated herein, the rocket engineis indicated generally at 10 and typically includes a chamber 12 whereincontrolled combustion takes place for the generation of high mass rateflow combustion gases. The chamber 12 delivers through a restrictedthroat portion 14 which exits into a conically divergent fixed nozzleportion 18. The extendible portion of the rocket nozzle extension isindicated generally by the numeral 20, and connects as indicated at 22in ring mounted manner at its smaller diameter end to the exit endportion of the fixed nozzle 18. The nozzle extension 20 consists of afirst section 24 which is joined along a fold line 26 to an outersection 28 which terminates at its outer end in an out-turned flangeportion 30.

As illustrated at FIGS. 1-7 herewith, the extendible nozzle section24/28 may be arranged to be deployed from its retracted or "stowed"position (as shown in FIGS. 1, 3) to its extended position (as shown inFIGS. 2, 7) by means of actuators 32 such as are disclosed for examplein U.S. Pat. 3,346,186. Such actuators 32 may be disposed at intervalsabout the nozzle 18, and fulcrumbed thereon such as by means of brackets34. As shown, at their extendible ends the actuators pivotally attach toa ring-like member 36 which is fixed by any suitable means to the flange30 of the extendible nozzle section 20.

As explained for example in U.S. Pat. No. 3,784,109, the extendiblenozzle section 20 may be fabricated of thin sheet lightweightheat-resistant material such as "columbium C-103"; and is adapted to beconvolute-folded back upon itself to assume the retracted conditionthereof as shown in FIGS. 1, 3, of the drawing herewith. Thus, thesection is thereby nested relative to the fixed nozzle structure so asto reduce the space required to house the assembly when inoperative.Upon operation of the actuators 32, as the latter extend they cause theconvoluted member 20 to unroll outwardly until it is finally extended ina position such as shown in FIGS. 2, 7, whereby the deployed nozzlesection provides a smooth slope continuation of the fixed nozzle section18.

As explained in U.S. Pat. No. 3,784,109, the frusto-conical nozzleextension 20 may be constructed by shear spinning it from a suitablecircular blank of sheet metal. The extension may then be telescopicallyrolled back upon itself to provide an inner convolution surrounded by anoutwardly spaced but somewhat parallel outer convolution joined by thefold section 26. Alternatively, the convolutions may be formedseparately and joined together as a unitary whole in the collapsedcondition as illustrated by FIG. 1 by means of welding or the like. Asillustrated at 38, a positional stabilizing and deployment controldevice may be optionally provided in the form of a lightweight ring offiller material, such as aluminum honeycomb or the like, in nestedposition between adjacent portions of the retracted nozzle portion 28and the stowed skirt 40. Preferably, this device is adapted to beheat-eroded away upon engine firing, or is segmented and may bespring-loaded for jettisoning ejection after release by opening of theskirt device 40.

In accordance with the present invention the payload/range performancecapability of an engine of this type may be substantially improved bythe addition of a deployable skirt such as is indicated generally by thenumeral 40. The device 40 comprises, when extended, a frusto-conicalshaped thin sheet metal sleeve, but which when first installed prior toengine firing is in the configuration as shown in FIGS. 1, 3, forcompact stowage thereof. Fabrication of the device may be effected byprocessing a thin sheet metal workpiece 42 as illustrated by way ofexample at FIGS. 14-17 herewith.

As shown therein, an arcuately shaped strip 42 of thin sheet metal (ofmetallurgical specifications as referred to hereinafter) is pressedbetween upper and lower die devices 43, 44, respectively, which arecomplementarily configured, so that the dies deform the workpiece toinclude creases extending transversely of the workpiece in the form ofupwardly extended ridges 45 in-between which are disposed downwardlydepressed valley portions 46. Note that the upraised ridge portions 45extend normal to the longitudinal edges of the workpiece; whereas thedownwardly projected valley portions 46 are paired in convergingconfigurations as best shown at FIG. 14. Incidental to this die-formingoperation the die members are also equipped to sever the work sheetalong lines 47 adjacent the edge of the work sheet where the lines 45-46converge; the creases 45-46 terminating at the inner ends of the cuts47. Alternatively, the dies may be arranged to press the creases 45downwardly, and the creases 46 upwardly.

Thus, when the work sheet exits from the die-forming/cutting operation,it will appear in a form as depicted at FIG. 16. The work sheet is thenpleat-folded upon itself progressively from one end thereof to the otheras shown at FIG. 17; such as by retention of one end of the work sheetin a suitable fixture while progressively press-feeding the body of thework sheet towards and against the progressively restrained portionsthereof. The cuts 47 facilitate this pleat-folding operation while atthe same time providing attachment platelets 48. This pleat-foldingoperation brings the opposite ends of the work sheet into abuttingrelation, whereupon they are butt-welded or otherwise fixed together;thereby fabricating the skirt into a flat annular form as shown forexample at FIG. 9. Incidental to the pleat-folding operation thepreviously formed cuts 47 enable the segmented portions thereof tospread slightly apart, thereby providing the "fan" of platelets 48 whichare adapted to be affixed to the rim portion 30 of the rocket engine byany suitable means such as welding, riveting, or the like. Thus, it willbe appreciated that the skirt device as initially pleat-folded willassume a " stowed" position interiorly of the engine nozzle sections 28,50 and 56, respectively, when attached thereto as shown for example atFIGS. 1, 3, 8, 12; whereat the skirt device adds little or nothing tothe packaging space requirement for the overall engine/nozzle unit priorto firing of the engine.

FIGS. 4, 5, 6, 7, illustrate progressively deployment of the enginenozzle/skirt combination incident to firing of the engine 10. Followingignition of the engine the actuators 32 thereof are operated so as toextend the nozzle 20 as illustrated progressively at FIGS. 3-7, asexplained for example in U.S. Pat Nos. 3,711,027 and 3,784,109.Incidental to this the filler ring 38 is either jettisoned orheat-eroded away (FIG. 6) and the skirt 40 is peripherally engaged bythe engine exhaust plume and thereby driven outwardly to assumethroughout the inner surface thereof a smoothly continuing extension ofthe conical slope form of the engine nozzle, as shown at FIGS. 2, 7.

FIGS. 8, 9, compositely illustrate adaptation of the skirt 40 of theinvention to a fixed nozzle type rocket engine wherein the nozzle 50 isof simple frusto-conical form and occupies the same space before andafter firing of the engine. The skirt 40 is in this case attached to theexhaust end of the nozzle 50 as indicated at 52 and is deployed from thestowed position thereof as shown in FIGS. 8, 9, to the expanded/extendedposition thereof as shown in FIGS. 10, 11, in response to pressuredeveloped by engine ignition gases impinging upon the skirt and forcingit to open.

FIGS. 12, 13, illustrate adaptation of the skirt 40 to an extendiblenozzle of the type shown for example in U.S. Pat. Nos. 3,711,027 and3,784,109, wherein the skirt 40 is attached as indicated at 54 to theexhaust end portion of the expandable nozzle section 56. When in itsstowed position before firing of the engine, as shown in FIG. 12, anengine nozzle cover 58 is detachably mounted upon the nozzle exhaust asexplained in the aforesaid patents. Hence, upon firing of the engine thenozzle is initially deployed from the position shown in FIG. 12 to theposition shown in FIG. 13, either by gases initially developed uponengine firing or by an auxiliary pressurized gas supply, as may bepreferred. The nozzle cover 58 is then jettisoned by the developed gaspressures, whereupon the engine exhaust plume engages the stowed skirtdevice 40 and drives it outwardly into its extended/expanded position asshown in FIG. 13.

The workpiece employed in fabrication of the skirt device of theinvention may be made of any suitable ductile, heat anderosion-resistant, metal or alloy, or other material. For example, ifthe anticipated working temperatures would not exceed 1,500° F. aductile steel may be employed. For temperatures between 1,500° F. and3,000° F. a columbium alloy may be preferred; and for temperatures above3,000° F. a tantalum alloy may be preferred. In any case, thecomposition/metallurgical specifics of the workpiece selected willdepend upon ductility/heat-resistant erosion/cost considerations.

I claim:
 1. The method of fabricating a skirt-like device for attachmentto the exit end of a rocket engine nozzle, said device being initiallyfolded for compact stowage relative to the engine nozzle and adapted tounfold upon engine firing for increasing both the length and exit enddiameter/area of the effective nozzle/skirt combination, said methodcomprising:a. cutting a workpiece of thin sheet heat-resistant ductilematerial into plan view arcuate form of such configuration that theworkpiece is then adapted to be creased and pleatfolded whereupon theopposite ends of the workpiece meet to be fixed together to provide askirt-like device which when unfolded and extended is of frusto-conicalform; b. deforming said workpiece so as to include suitable creasestherein running generally transversely of the workpiece sequentially ofthe length of the workpiece, said creases being alternately directed inopposite directions with the inwardly directed creases being arranged inconverging pairs, each converging pair being separated from the nextpair by a single outwardly directed crease; c. progressivelypleat-folding the workpiece from one end thereof to the other, and then;d. fastening the opposite ends thereof together to form the device intoa generally flat annular configuration;whereby the device is adapted tobe attached along its outer periphery to the exit end of an enginenozzle with the body of the device in a stowed position relative theretooccupying no substantial space outside of the engine nozzle; wherebyupon engine firing, the device may deploy to provide an effective enginenozzle/skirt combination of increased length and exit diameter/area. 2.The method as set forth in claim 1, wherein said workpiece is alsomultiple-cut inwardly along one edge thereof to provide whenpleat-folded a series of platelets fanning outwardly from thepleat-folded portion of the device for attachment to the exit end of theengine nozzle.
 3. The method as set forth in claim 1, wherein saidworkpiece is formed of ductile steel.
 4. The method as set forth inclaim 1, wherein said workpiece is formed of columbium alloy.
 5. Themethod as set forth in claim 1, wherein said workpiece is formed oftantalum alloy.
 6. The method of fabricating a skirt-like device forattachment to the exit end of a rocket engine nozzle, said device beinginitially folded for compact storage relative to the engine nozzle andadapted to unfold upon engine firing for increasing both the length andexit end diameter/area of the effective nozzle/skirt combination, themethod comprising:a. cutting a workpiece of thin sheet heat-resistantductile material into plan view arcuate form of such configuration thatthe workpiece is then adapted to be creased and pleatfolded whereuponthe opposite ends of the workpiece meet to be fixed together to providea skirt-like device which when unfolded and extended is offrusto-conical form; b. deforming said workpiece so as to includesuitable creases therein running generally transversely of the workpiecesequentially of the length of the workpiece, said creases beingalternately directed in opposite directions with the inwardly directedcreases being arranged in converging pairs, each converging pair beingseparated from the next pair by a single outwardly directed crease; c.progressively pleat-folding the workpiece from one end thereof to theother while substantially within a single plane, and then; d. fasteningthe opposite ends thereof together to form the device into a generallyflat annular configuration;whereby the device is adapted to be attachedalong its outer periphery to the exit end of an engine nozzle with thebody of the device in a stowed position relative thereto occupying nosubstantial space outside of the engine nozzle; whereby upon enginefiring, the device may deploy to provide an effective enginenozzle/skirt combination of increased length and exit diameter/area.